The present invention relates to an inflatable seatbelt system having a webbing at least a part of which is formed in the shape of a bag and which is maintained in a strap-like configuration under normal circumstances but, when an emergency situation occurs, inflates by the action of a gas supplied from a gas generating device. More particularly, the present invention relates to an inflatable seatbelt system designed to protect the occupant from a large impact applied in the lateral direction of the vehicle when it comes into collision sideways or other similar emergency situation occurs.
Hitherto, seatbelt systems have been attached to the seats of many vehicles, for example, automobiles. A typical seatbelt system is arranged to restrain the occupant's body by a webbing upon the occurrence of an emergency situation, e.g., a collision of the vehicle, thereby protecting the occupant from injury which would otherwise be done to him or her by collision with a part of the vehicle body. In such a seatbelt system, however, the width of the webbing, which constitutes a belt for restraining the occupant's body, is not so large. Therefore, the occupant's body locally receives a relatively heavy load when restrained by the webbing.
Under these circumstances, a variety of inflatable seatbelt systems have been proposed in which the webbing is formed in the shape of a bag, and under normal circumstances, the bag-shaped webbing is maintained in a strap-like configuration so as to function as an ordinary seatbelt, whereas, when an emergency occurs, the bag-shaped webbing is inflated by a gas introduced thereinto from a gas generating device so as to function as an air belt whereby the occupant's body is received by the inflated webbing. For example, see Japanese Patent Application Laid-Open (KOKAI) Nos. 47-26830 and 49-88220. Such an inflatable seatbelt system allows the kinetic energy of the occupant's body to be received by the webbing having a wider area. Thus, the load is dispersed, and hence the occupant's body receives a relatively light load. Accordingly, the occupant is protected even more effectively.
When inflating, the webbing shortens longitudinally and, at the same time, increases in thickness. Consequently, the webbing presses the occupant's body against the seat by an amount corresponding to the increase in the thickness. That is, since the length of the webbing shortens and the thickness thereof increases due to the inflation of the webbing, it is possible to obtain a webbing pull-in effect similar to the effectiveness obtained when the webbing is actually pulled in. Accordingly, the inflatable seatbelt system makes it possible to obtain initial restraining force similar to that provided by a pretensioner.
With the initial restraining force, the inflatable seatbelt system completely restrains the occupant's body during a crashable zone, i.e., a period between the time when a vehicle comes into collision and the time when the front part of the vehicle, gradually crashing, reaches the occupant's body. Accordingly, it is possible to make good use of the crashable zone.
If it is intended to provide a rear seat with an air bag system as is provided for the occupant seated in the front seat, the air bag system must inevitably be provided on the front seat, which lies forwardly of the rear seat. However, if the air bag system is provided on the front seat, it is difficult for the air bag system to protect the rear seat occupant properly and effectively because the position in the longitudinal direction of the front seat depends on the occupant seated therein and the reclining position also differs according to circumstances. Accordingly, the above-described inflatable seatbelt system is particularly effective as a safety device for the rear seat.
However, most of the conventional inflatable seatbelt systems, including those disclosed in the above-described publications, are designed for an emergency situation where high deceleration is applied in the longitudinal direction of the vehicle, for example, when it has a head-on collision. Almost no consideration has heretofore been given to an occasion on which a large impact is applied in the lateral direction of the vehicle, for example, when it comes into collision sideways.
Therefore, the conventional inflatable seatbelt systems cannot always be said to be capable of satisfactorily and reliably protecting the occupant when a large impact is applied in the lateral direction of the vehicle.